来自葡萄牙IGC研究所和纽约冷泉港实验室的科学家们已经描述出植物花粉粒中预防转座子引起的突变的机制。
转座子或跳跃基因在现有的基因组中十分常见。例如，转座子在玉米基因组内比例超过70%。激活转座子可能会引起有害的突变，因此，转座子的激活需要严格控制。如果类似的有害突变发生在有性生殖细胞中，会将损害传递给下一代并蔓延至整个族群。
在花粉粒中，精细胞是由大型的伴细胞保护的。伴细胞向精细胞提供能量和营养物质，并在授精过程中推动其向目标前进。科学家们发现，伴细胞也向精细胞提供指示，使其DNA免受损害，从而帮助精细胞稳定地传递基因组信息至下一代。这种提示是以小干扰RNAs（siRNA）的形式存在的，通过RNA干扰使转座子沉默。（生物谷Bioon.com）
生物谷推荐原始出处：
Cell, 6 February 2009 doi:10.1016/j.cell.2008.12.038
Epigenetic Reprogramming and Small RNA Silencing of Transposable Elements in Pollen
R. Keith Slotkin1,Matthew Vaughn1,Filipe Borges2,Miloš Tanurdžić1,Jörg D. Becker2,José A. Feijó2,3and Robert A. Martienssen1
1 Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA
2 Instituto Gulbenkian de Ciencia, Centro de Biologia de Desenvolvimento, 2780-901 Oeiras, Portugal
3 Departamento de Biologia Vegetal, Faculdade de Ciencias da Universidade de Lisboa, Lisboa, 1700 Campo Grande, Portugal
The mutagenic activity of transposable elements (TEs) is suppressed by epigenetic silencing and small interfering RNAs (siRNAs), especially in gametes that couldtransmit transposed elements to the next generation. In pollen from the model plant Arabidopsis, we show that TEs are unexpectedly reactivated and transpose, but only in the pollen vegetative nucleus, which accompanies the sperm cells but does not provide DNA to the fertilized zygote. TE expression coincides with downregulation of the heterochromatin remodeler DECREASE IN DNA METHYLATION 1 and of many TE siRNAs. However, 21 nucleotide siRNAs from Athila retrotransposons are generated and accumulate in pollen and sperm, suggesting that siRNA from TEs activated in the vegetative nucleus can target silencing in gametes. We propose a conserved role for reprogramming in germline companion cells, such as nurse cells in insects and vegetative nuclei in plants, to reveal intact TEs in the genome and regulate their activity in gametes.
